1. Field of the Invention
The present invention relates to an organic electroluminescent display using a plurality of organic electroluminescent devices.
2. Description of the Background Art
With the recent diversification of information equipment, there is a growing need for flat panel displays that require lower power consumption than commonly used CRTs (cathode ray tubes). As one of the flat panel displays, organic electroluminescent devices (hereinafter abbreviated to organic EL devices) with such features as high efficiency, thinness, lightweight, and low viewing angle dependency, have attracted attention. Displays using such organic EL devices are actively being developed.
An organic EL device is a self-emitting type of device. In the organic EL device, an electron injection electrode and a hole injection electrode inject electrons and holes, respectively, to a luminescent portion, where the injected electrons and holes are recombined at a luminescent center to bring organic molecules into excited states, and the organic molecules fluoresce when return from their excited states to ground states.
Organic EL devices can emit a variety of colors of light depending on the selection of fluorescent materials which are the luminescent materials, which makes them increasingly promising for applications in displays such as a multi-color display or full-color display. Since the organic EL devices can emit light on a surface at low voltage, they can also be utilized as the backlights for liquid crystal displays, etc. Applications of such organic EL devices to small displays such as digital cameras or cellular phones are currently in the development phase.
An organic EL device typically has a structure that includes a hole injection electrode, hole injection layer, hole transport layer, light emitting layer, electron transport layer, electron injection layer, and electron injection electrode in order on a substrate. The hole injection layer, hole transport layer, light emitting layer, electron transport layer, and electron injection layer will hereinafter be referred to as organic layers.
In realizing a full-color display with such organic EL devices, it is necessary to form each of the organic EL devices independently, which emit the three primary colors of red, green, and blue, respectively. This makes the fabrication processes complicated.
In order to avoid such complication of the fabrication processes, a combined use of a white light emitting device and color filter layers that transmit the monochromatic lights of three primary colors makes a full-color display possible (refer to JP H11-260562 A, for example). Such a white light emitting device, which contains a blue light emitting material and an orange light emitting material, can simultaneously emit blue and orange lights produced by the blue and orange light emitting materials so as to realize the emission of white light. In the emission spectrum of the above-mentioned white light emitting device, there are emission peaks for the blue and orange, respectively.
However, these two emission peaks are so broad that an emission peak for the green is hardly present. This results in lowered color purities of red, green, and blue, which therefore prevents emissions of red, green, and blue lights with high color purities from being attained.